The present invention relates generally to the field of gas turbine engine airfoils. More particularly, one embodiment of the present invention defines a high temperature airfoil including a metallic spar with a plurality of replaceable tiles coupled thereto. Although the present invention was developed for use in a gas turbine engine, certain applications may be outside this field.
A gas turbine engine is typical of turbo machinery in which the concept described herein may be advantageously employed. It is well known that a gas turbine engine conventionally comprises a compressor for compressing the inlet air to an increased pressure for combustion in a combustor chamber. A mixture of fuel and the increased pressure air is burned in the combustor chamber to generate a high temperature gaseous flow stream for causing rotation of the turbine blades within the turbine. The turbine blades convert the energy from the high temperature gaseous flow stream into kinetic energy, which is utilized to turn a propeller, fan or other device. Further, the high temperature gaseous flow stream may be used directly as a thrust for providing motive power, such as in a turbine jet engine.
A long recognized need by many gas turbine engine designers is to attain higher operating temperatures in order to achieve both a greater thermodynamic efficiency and increased power output per unit of engine weight. Theoretically, a gas turbine engine would operate at stoichiometric combustion in order to extract the greatest possible energy value from the fuel consumed. However, temperatures at stoichiometric and even near stoichiometric combustion are generally beyond the endurance capabilities of traditional metallic gas turbine engine components. Consequently, significant efforts have focused on developing enhanced cooling techniques and temperature and oxidation resistant metals for use in components of the engine, which are exposed to the highest temperatures. More specifically, cooling techniques and high temperature metals have been developed for many components such as combustion chambers, turbine nozzles, and turbine blades.
An alternate approach to the attainment of higher operating temperatures in a gas turbine engine involves the use of components formed from ceramic materials. Ceramic components are better able to withstand the high temperature oxidizing environment within the gas turbine engine. However, while many ceramic materials exhibit superior high temperature strength and oxidation resistance, they have historically been difficult to utilize in gas turbine engines because of a comparatively low tensile fracture strength.
Heretofore, there has been a need for light weight high temperature gas turbine engine components. The present invention satisfies this need in a novel and unobvious way.